In brief:
Vagal Response

However, there is a condition that can cause both nausea and arrhythmia (particularly slow heart rate), and that is called a vagal response. This is an abnormal reflex response which causes the heart rate to abnormally slow, and also has concurrent symptoms of nausea and/or "cold sweats" and/or lightheadedness.

In brief:
Vagal Response

However, there is a condition that can cause both nausea and arrhythmia (particularly slow heart rate), and that is called a vagal response. This is an abnormal reflex response which causes the heart rate to abnormally slow, and also has concurrent symptoms of nausea and/or "cold sweats" and/or lightheadedness.
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I agree with Dr. Min and would add that the irregular blood flow caused by certain irregular rhythms OR low blood pressure caused by very fast heart rhythms can both also cause nausea. We see this rather frequently as a symptom of arrhythmia.